Electromagnetic relay



April 25, 1950 H. AKROYD 2,505,225

ELECTROMAGNETIC RELAY Filed May 26, 1945 A Home y Patented Apr. 25, 1950 landil assignnrto-0ldham 8z Son Limited, Denton, near-f Manchester, England;-,a British; com- Application-May 26, 1945, Serial No; 595,908 In Great Britain April '21, 1944' This invention relates to -electromagnetic re l'ays of the type in which an electric contact/is closed when the relay" is' not energised is openedwhen the relay i'senergised Relays of this type; for? certainpurposes; are required tooperate both to= close and to open the contact for a variatiorrinthe currentthr'ough the relay which is a fractionrof the normal current; Forinst'ance a relay in acircuit in which,

say, 50 volts are normally on the relay; may

be required -to closeits contact if the volts drop to 30, and to openitsicontact if. they rise to 40.

The adjustm'eritneeded to'causea relay to fulfil such conditions usually: consists in: varying: the

tension of the spring operating :toipulltthe armature away firom the pole-pieces The object of the invention is a relay which canbeadjusted to operate-with a predetermined variationof current without varying the spring tension: A further object is a relay of simple construction provided wit-h the required means of adjusting its operating limits:

According to thed-nvention; a: relay of the type described; havinga-fixew' contact and a-contact moving with-thearmaturejis providedwith means for adjusting the air-gap of the armature when the armature is in attracted position and independent means for adjusting the air-gap when the contacts are closed.

Conveniently, the electromagnetic relay according to the invention comprises a moving contact which is adjustable in position relatively to the armature. The moving contact may be mounted on a flexible member connected with the armature at one end, and adjusting means may be provided for bending the flexible member to or from the armature.

In one practical form of the invention the electromagnetic relay comprises an adjusting screw traversing the armature or piece attached thereto and adapted to abut against the polepiece attached thereto, and a nut on the said screw engaging the flexible member and adapted to bend it to or from the armature.

In the accompanying drawings, which show by way of example three constructional forms of a relay according to the invention,

Figure 1 is a section of a relay and Figures 2 and 3 are part sections of alternative forms of relay.

In the drawings like reference numerals designate similar parts.

Referring to Figure 1, the magnetcore I is provided with a, winding 2 and iron end pieces 3 and 4, the latter forming a pole-p'iece'at 5. An

armature t'is: pivoted at I.'to=the'--endzpiece 3' and is: drawn away from the-pole-piecei-fi' bytherspring 8'. A flexible member 9 carrying the: moving contact this attachedito the armature 6 at M. Thebrelay is carriedron a, baseiepla'te (not shown) by brackets: I2, and a bracket I23 carries the fixed contact I4; Ascrew I5. passes through the armature 5 so; that: its;end abutsromtherpolepiece 5. The screw I B- passesf thmughfajslot in the end of the'flexiblemember' ili, .and:a nut I6 onthescrew lfi 'bears on it.

The: relayis showntin energised-5 position, with its 'contacts Iii-"and 1I 4i open, By moving trier-screw I-5'more .or' less through the armaturexfigthe width ofthe'azir-gap. at t may be adjusted and; thereby the relay may be adjustedito operate to'close' its contacts I'll' I'42for a predeterminedxvalueof the current through its wind'ing lessithan theinormal current; When this adjustmenthasbeenefiected, the screw I5 may be held stationary and the. nut I 6 turned to vary the distance ofthemoving contact Ill from the armature, to adjustithe width of 'theai-r-gap at 5 whena-the'rel'ay is; de-energised, and-thereby the relay may be' adjusted ito operate to open itscontacts for" a-predetermined value of the current, without disturbing the previously made adjustment for operation to close the contacts.

If, on the other hand, the adjustment of the air-gap when the contacts are closed is correct, and it is desired to alter the adjustment of the air-gap when the contacts are open, this may be effected by turning together the screw I5 with its nut I6. Thereby the latter adjustment is made without affecting the former adjustment. The two adjusting means are, therefore independent, in the sense that they enable either adjustment to be made without affecting the other.

The spring 8 acts at a point close to the pivot I, so that its tension is appreciably the same for the two positions of the armature.

Figure 2 shows an alternative form of the adjusting means, in which the screw I5 for adjusting the air-gap when the contacts are open is in a bracket I! attached to the end piece 4 to which it forms a lateral extension, while the adjustment of the air-gap when the contacts are closed is efiected by the screw I8 in a piece I9 attached to the armature and overlapping the said extension, against which piece I9 the screw I5 abuts. The fixed contact I4 is shown nonadjustable in its bracket I3, but it may be made adjustable, as in Figure 1, by means of the screw 20.

Figure 3 shows another alternative form, in which the screw I5 is disposed as in Figure 1, while the moving contact is on a screw 2| in the armature 6.

In practice it is generally required that the relay shall close and open its contacts as a result of small current variation and for this the change in air-gap in the two positions of the armature is made very small. It has been exaggerated in the drawings for the sake of clearness.

I claim:

1. An electromagnetic relay comprising in combination, a pole-piece, an armature pivoted for attraction towards the pole-piece when the relay is energised, a pair of co-operating electrical contacts to be opened when the relay is energised, one of said contacts being stationary and the other movable with and adjustable relatively to the armature, a first adjusting means to maintain a permanent air gap between the armature and the pole-piece and for regulating the air gap when the armature is attracted, and a second adjusting means for independently regulating the said air gap when the contacts are closed.

4 2. An electromagnetic relay comprising in combination, a pole-piece, an armature pivoted for attraction towards the pole-piece when the relay is energised, a pair of cooperating electrical contacts to be opened when the relay is energised, one of said contacts being stationary and the other movable, a resilient carrier for the movable contact said carrier being mounted on the armature for movement therewith, a first adjusting means movable relatively to said carrier to maintain a permanent air gap between the armature and the pole-piece and for regulating the air gap when the armature is attracted, and a second adjustable means for independently regulating the said air gap when the contacts are closed.

3. An electro-magnetic relay as claimed in claim 2, wherein the first adjusting means comprises a screw passing through the armature to abut 0n the pole-piece and the second adjusting means comprises a nut on the screw to engage 4 said carrier, whereby adjustment of the movable contact relatively to the armature may be effected without affecting said air-gap or adjustment of the air gap may be effected without affecting the position of the movable contact relatively to the armature.

4. An electromagnetic relay as claimed in claim 2, wherein th first adjusting means comprises a first screw passing through an extension of the pole-piece to abut on an extension of the armature and the second adjusting means comprises a second screw passing through said extension of the armature and engaging said carrier, whereby adjustment of the movable contact relatively to the armature may be effected without affecting said air-gap or adjustment of the air gap may be ,eiiected without affecting the position of the REFERENCES CITED The'following referencesare of record in the file of this patent:

UNITED} STATES PATENTS Number Name Date 476,330 Thomson June 7, 1892 708,539 Fell Sept. 9, 1902 825,830 Heinze July 10, 1906 1,311,460 Patten July 29, 1919 1,442,489 Mallory Jan. 16, 1923 1,701,634 Putt Feb. 12, 1929 Lear et al Jan. 30, 1934 

